Multiplex broadcast system



Aug. 1930. E. R. TAYLOR ET 1,772,165

xumxrwx BROADCAST SYSTEM I Filed Aug. 17. 1926 3 Sheets-Sheet .1

Ill Mum I U I m I I Q A TTORAE y Aug. 5, 1930. E. R. TAYLOR 1,772,155

MULTIPLEX BROADCAST SYSTEM Filed Aug. 17. 1926 s Sheets-Sheet 2 INVENTORS E11. Yhylor 31 azzmw Aug. 5, 1930. E. R. TAYLOR ET AL 1,772,165

I IULTIPLEX BROADCAST SYSTEM Filed Aug. 1'7, 1926 3 Sheets-Sheet 3 1N VENTORS (7 )1 TTORNE y Patented Aug. 5, 1930 UNITED STATES PATENT OFFICE EDMUND R. TAYLOR, OF NEW YORK, N. Y., AND OSCAR B. HANSON, OF ROSELLE, NEW JERSEY, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A

CORPORATION OF NEW YORK MULTIPLEX BROADCAST SYSTEM Application filed August 17, 1926. Serial No. 129,884.

This invention relates to multiplex broadcasting systems, and particularly to arrangements in such systems for interconnecting a plurality of sources of news, music or the like with aplurality of transmitting stations so that the programs originating at said sources maybe simultaneously broadcast by said transmitting stations.

This invention results from longcontinued experimentation with broadcasting systems. The first broadcasting system involved but one studio or program source and one transmitting station. These were permanently connected so that when the transmitting station was in operating condition all the sounds which were made in the studio were audible to the radio audience. This was soon found to be objectionable because certain sounds incidental to arranging the artists, etc., proved to be both disconcerting and displeasing. Accordingly a single and control arrangement was evolved which disconnected the studio from the transmitting station when it was not desired that the sounds in the studio be heard by the radio audience. This was found to result in objectionable delays while one group of artists was leaving the studio and another was entering and preparing for the transmission of the next program. At a later time, this led to the provision of two or more adjacent studios so arranged that while one group of artists was broadcasting another group of artists could be arranging themselves in another studio and preparing to broadcast.

Almost from the beginning of the period of experimentation it was felt desirable to broadcast programs originating in one location simultaneously through two or more transmitting stations. At any given time all of the transmitting stations might be transmitting the same program, i. e., the program originating at one studio, and at other times various transmitting stations might be transmitting different programs, i. e., programs originating at different studios. At first, this resulted in a rather complicated switching mechanism betwen studios and transmitting stations. Tlie switching of studios and transmitting stations was accomplished mainly by means of mechanically interlocking switches. This system soon proved to beinadequate as the number of studios and transmitting stations increased, and moreover, it was difficult to operate. It brought about a considerable loss of time when different groups of stations and studios were being set up, and furthermore, it resulted in the broadcasting of objectionable switching noises due to the complexity of the system. At times it also resulted in the broadcasting by one transmitting station of a program intended for another transmitting station, occasionally simultaneously with the proper program. The system described herein results from improvements made while experimenting with the old systems, and is designed to overcome the difficulties of the old systems some of which are mentioned hereinabove. The present system is simple so that a non-technical man, such as an announcer, may operate it rapidly and smoothly.

Whereas the system is primarily designed to-inter-connect a plurality of studios and a plurality of transmitting stations, it is equally applicable whenever a number of sources of sound are to be connected electrically to a number of other points. Obviously these points may be radio transmitters, public address systems, wire broadcast systems, etc. For the sake of convenience these will all be referred to herein as transmitting stations.

It will be understood that this system is particularly applicable where such connections must be made without appreciably changing the gain-frequency characteristics of the circuits involved.

In accordance with the present ractice it is often desirable to operate several broadcasting studios in connection with anumber of transmitting stations. The interconnecting system to accomplish this is described herein merely for the sake of illustration, and is so arranged that any one of the studios may be connected to any one of the transmitting stations, no two of the studios being connected to any one transmitting station at the same time. This is accomplished in a manner such that the audiences of the transmitting stations do not hear any of the switching noises and do not observe any appreciable delays between selections, or that any other program is being transmitted by any other transmitting station except the one the audiences are scheduled to receive.

It will be understood that one or more of the studios may be located in close proximity to the switching point and that one or more of the other studios may be located at a point or points widely remote therefrom and connected thereto by suitable signaling circuits, or by other transmission paths. It will be further understood that the studios, control room and transmitting stations shown herein may be widely separated from each other and may be connected by any suitable medium or media, such as wire lines or radio circuits, within the scope of this invention.

While the nature of the invention will be pointed out with particularity in the appended claims the invention itself, both as to its objects and features, will be better understood from the detailed description hereinafter following when read in connection with the accompanying drawing, in which Figures 1, 2 and 3 schematically disclose the general principles of the invention, and in which Figs. 4 and 5, when placed side bv side, show one application of the principles of the invention to a multiplex broadcasting system.

Referring to Fig. 1, there are shown four studios, A to D, inclusive. The circuits from these studios converge in a control room CR, which may be, for example, adjacent to the studios. In this room the signals from the studios are amplified and distributed to the various radio transmitters RT to RT. inclusive. The arrows on the circuits between the studios A to D, the control room CR and the radio transmitters RT to RT, indicate the direction of transmission of the program matter. Obviously the studios A to D and the ratio transmitters RT to RT may be adjacent to the control room CR and may be connected thereto by local or, perhaps, by long distance telephone lines or other transmitting media. Whenever it becomes desirable to supplement a program originating at a studio with material originating at a remote point known as a pick-up point, such as a theater, the circuits from the remote pick-up point may be brought into the control room CR and then into one of the studios, so that the circuits may be controlled at that studio and appropriate announcements made whenever necessary by the announcer in that studio. 'lhese circuits from pick-up points have become known as nemo circuits, and they will be described in greater detail hereinafter. Although the system has been shown to include four studios and five radio transmitters, it will be understood that the invention is not to be limited in that respect, but that any number of studios may be connected to any number of radio transmitters so that the programs from the various studios may be simultaneously broadcast by the various radio transmitters.

Fig. 2 shows three studios, A, B and C and the corresponding signaling circuits terminating in channel (horizontal) bus bars having the amplifiers A A: and A associated with these bus bars, respectively. These channel (horizontal) bus bars may be connected by relays (not shown) to station (vertical) bus bars and the associated amplifiers A to A inclusive, one of these amplifiers corresponding to each of the station (vertical) bus bars. The station (vertical) bus bars are connected to the transmitting stations TS to TS.;, inclusive. Each relay, as will be shown in greater detail hereinafter, is so arranged that it may be controlled from the studio associated therewith, and is further arranged so that no two channel (horizontal) bus bars may be connected to the same station (vertical) bus bar and the corresponding amplifier and transmitting station at the same time. In other words, the system is so arranged that any studio may be connected to any transmitting station whenever that transmitting station is not already connected to some other studio. Moreover, means (not shown) are provided so that the operating condition of any transmitting station is constantly indicated in the studios and in the control room. Thus as soon as the program is finished in one studio the transmitting station may be connected to receive the program of another studio without any appreciable loss of time.

In Fig. 2 a number of dotted and undotted circles are shown to represent the various relays, the dotted circles indicating operated relays and the undotted circles indicating unoperated relays. In this particular arrangement the studio A is connected to the transmitting station TS through the corresponding amplifier A The studio B is connected to the transmitting stations TS and TS through the corresponding amplifiers A and A respectively. And studio C is connected to the transmitting station TS through the corresponding amplifier A No studio is connected to the transmitting stations TS, and TS,. It is to be particularly noted that no one of the transmitting stations TS to TS,, inclusive, is connected to more than one studio.

In Fig. 3 the system is shown schematically in somewhat greater detail. In this figure only two studios A and B are shown, merely for the sake of simplicity, and the studios may be connected to either one of two transmitting stations. In studio A there are shown, for the sake of simplicity, only two transmitters or microphones, one for the program and one for the announcer, and control equipment CE for connecting the output of either of these transmitters to a control room amplifier A, corresponding to studio A and its associated equipment. The studio control equipment will be described in greater detail in connection with Figs. 4 and 5. lVhile the control room amplifier A has been shown as located at the control room this amplifier may, however, be located at the studio. This control room amplifier A has a main relay MR associated therewith in order to place the output of the control room amplifier A upon a channel bus bar CB There are also two line relays LR and LE one corresponding to each transmitting station, so that the channel bus bar CB and hence the output of the control room amplifier A, may be connected to either of the transmitting stations. Moreover line amplifiers A and A are shown, each of these amplifiers corresponding to one of the transmitting stations. The line relays LR and LR, are connected to the studio control equipment CE through the channels 21 and 22, respectively. By means of these channels the output of the control room amplifier A, and consequently the output of studio A, may be controlled through interlocking devices (not shown) so that the output of the control room amplifier A may be connected to either or both of the transmitting stations, if that transmitting station, or stations, is not connected to another studio, such as studio B. In other words, the interlocking devices (not shown) prevent the connection of more than one studio to one transmitting station at the same time. The control equipment in each studio may, of course, be located on a suitable control panel in that studio so as to be readily accessible to the announcer thereat. The main relay MR is connected to the studio control equipment 0E through a channel 23 so that the entire output of studio A may be quickly cut off. A nemo circuit is also provided in this arrangement for connecting an outside pick-up point with the studio control equipment so that the program of the pick-up point may be controlled at the studio. The apparatus for studio B is similar to that for studio A and therefore the description of the apparatus for studio B need not be repeated herein.

Figs. 4 and 5 show one embodiment of a multiplex broadcasting system to which the principles of this invention have been applied. In this system there are shown a plurality of studios A, B and C, and a plurality of transmitting stations comprising radio transmitters ST to ST inclusive, and a plurality of radio antennae TA to TA.,, inclusive, corresponding, respectively, to radio transmitters ST to ST... These studios and transmitting stations are interrelated so that the programs originating at these studios may be simultaneously broadcast by the transmitting stations, the system being so interlocked that no two studios may be connected to any one transmitting station at the same time. Each studio has a plurality of control relays, one corresponding to each of the transmitting stations. Accordingly, there are four control relays R to R R to R and R to R at the studios A, B and C, respectively. Some of the apparatus for connecting one studio with a particular transmitting station is located at that studio and the rest of the apparatus is located at the control room. Each studio has a program microphone and an announcers microphone. Moreover a nemo circuit is connected to each studio so that the program from some distant pick-up point may be brought into the studio in order to be transmitted throu h an appropriate transmitting station. T e program microphone MP MP MP the announcers microphones MA MA MA,, and the nemo circuits NC N 0 and N6 correspond, respectively, to studios A, B and C. Switches K and K K and K K and K are also located at the respective studios so that any one or more of the transmitting stations may be transferred by these switches to one or the other of the studio microphones, or to the microphone at some pickup point connected to the corresponding nemo circuit. Studios A, B and C terminate in studio bus bars SB SB and SE respectively, and the transmitting stations are connected through line amplifiers LA to LA,, inclusive, to corresponding channel bus bars (LB to CB inclusive.

For the sake of convenience the course of transmision from one of the studios, such as studio A, to one of the transmitting stations, such as that associated with the channel bus bar CB will now be considered in greater detail. A microphone control panel CP is located at studio A, this control anel adjoining the program microphone M 1 and the announcersmicrophoneMA Suitablemeans are associated with the microphone control panel CP for feeding current from a battery (not shown) to either or both of these microphones and other means are provided for observing the magnitude of the current fiowing from the battery through the particular microphone connected to the control panel CB It will be understood that these microphones may be of any well known type, such as, for example, a carbon transmitting microphone or a condenser microphone with its associated amplifier. I

The circuits connected to the microphone control panel CP have become known as the program and announcers circuits. These circuits are connected, respectively, to the lower contacts j and 7a of the switches K and K However it will be understood that equipand indicate to the announcer circuit NC, with the amplifier CA,.

ment at studios B and C is similar to that at studio A and the description of equipment at studio A applies equally well to studios B and C. A nemo circuit NC, is connected to the contacts a and b of the switch K Switches K, and K, are so arranged as to connect the program microphone MP the announcers microphone MA, or the nemio circuit NC, with the input of an amplifier CA, at the control room.

Three lamps, L,,,, L,, and L, at studio A are also operated by the switches K and K whether switches K and K, have been operated to connect the program microphone MP,, the announcers microphone M1 or the nemo This will be described in greater detail hereinafter.

The main transmission path may be followed from the contacts 6 and f of the switch K through the amplifier CA, at the control room, which is terminated in a suitable impedance, PT,, through the inner contacts made by armatures Z) and c of the relay R to the studio bus bar 813,. The main relay R functions to open the circuit between studio A and the corresponding bus bar SB, at times when it is considered undesirable to transmit that which is taking place at the studio. A volume indicator L1, is bridged across the main transmission path between the output of the am )lifier CA, and the terminating impedance T, to indicate the transmission volume after am lification. The value of the impedance P is low as compared to the impedance of input of the amplifiers LA, to LA, inclusive. Thus, when one amplifier, as. for example, the amplifier LA,, is connected to the studio bus bar $13,, other amplifiers, such as LA LA or LA,, may be connected thereto, or disconnected therefrom, without appreciably afiecting the energy transmitted by the amplifier LA,. This is so because most of the power transmitted by the amplifier CA, is being expended in the low impedance PT, and very little in the input of each line amplifier. In order to minimize the possibility of cross-talk between studio bus bars or channel bus bars when studio bus bar SB, is disconnected from the amplifier 0A,, a contact is closed by an armature d of the main relay R which puts a short circuit across the studio bus bar $13,, so that when the main relay R is not energized the line relays LR, to LR,, inclusive, similarly become short-circuited so that these line relays are unable to receive any program, thus preventing any voltages, which may be induced in these circuits, from being impressed upon the input of any line, amplifier, and hence amplified, causing ob ectionable cross-talk or interference. The operation of the line relays LR, to LR, will be given in greater detail in the description hereinafter following.

The system is so laid out that any studio may be connected with one or more transmitting stations simultaneously, and similarly, any transmitting station may be connected with any studio. One of the distinguishing features of the invention is an interlocking arrangement which prevents any one transmitting station from being connected to more than one studio at the same time. This is absolutely essential to prevent confusion between programs, and is an essential feature of the entire control system. It seems hardly necessary to state that failure to provide an interlocking arrangement would permit the tying together of two or more studio bus bars and corresponding studios to the same transmitting station. Moreover, line relays LR, to LR,, LR, to LR,, LR," to LR,", associated with the studios A, B and C, respectively, are so arranged as to prevent any one transmitting station from being connected to more than one studio at the same time. Failure of operation. or improper operation of the relays LR,, LR, and LR," would permit the transmitting station associated with the channel bus bar CB, to be connected to the studios A. B and C, simultaneously. Similar undesirable effects follow the failure of the other line relays.

Another feature of this invention is the provision of a signaling system throughout the studios and the control room to keep the announcers at the various studios and the operator at the control room continuously advised of the manner in which the studios are connected with the various transmitting stations. It is another feature of this invention to provide means for the announcer at any studio to be able to connect his studio to one or more of the transmitting stations so that after his studio has been connected to these transmitting stations no other studio can be connected to the same transmitting stations at the same time. Thus, the announcer at any studio has at his disposal apparatus for picking up and releasing the various transmitting stations, and he has also a signaling system which keeps him continuously advised as to whether or not these transmitting stations are already connected to his studio or to one of the other studios. These features will be described in greater detail hereinafter.

In studio A the keys K, and K,, which are momentary contact keys, control the operation of relay R,. By closing key K, the relay R, becomes energized by the flow of current through the winding of said relay from a battery E the circuit including the armature of the relay IR,, conductor 21, key K,, the winding of the relay R,, key K key K,,, conductor 22, key K and ground. As the winding of the relay R, becomes energized its armature A closes a cont act 0 so that the winding of the relay R, receives current also from a battery B this circuit including key K conductor 23, key K,,, the armature A and the contact 0 of the relay R,, the winding of the relay R,, key K key K,,, conductor 22, key K and ground. After contact 0 of the relay R, has been closed by the armature A of that relay, relay R, remains energized even after key K, is released. Shortly after contact 0 of the relay R, is closed by armature A, another contact 02 is closed by armature A. Current then flows from the battery B through the winding of the relay 1B,, this circuit including the battery 13,, the key K,-,, conductor 23, key K1,, the armature A of the relay R1, contacts 0 and d of relay R,, conductor 24, the winding of the relay IR, and ground. Thus, as the armature A of the relay R, closes its contact 03, the relay IR, becomes energized so that its armature opens the contact associated therewith, disconnecting battery B, from the winding of the relay R,. et the winding of the relay R, remains energized by the flow of current from the battery B, through the circuit including key K the conductor 23, the key K,,, the armature A, the contact a and the winding of the relay R,. key K key K,,, conductor 22, key K and ground. However, current may flow through the keys K, and K," in the studios B and C, respectively, only when the relay IR, is deenergized. After relay R, has operated to close' contact d and after relay IR, has become energized, the relays R, and R, in the studios B and C cannot become operated by keys K, and K," in studios B and C, respectively until the relay IR, has become deenergized again.

The winding of the relay LR, is in parallel relationship with the Winding of the relay B, through the conductor 25, and therefore the energization or deenergization of the relay R, causes a corresponding action of the relay LR,. The armatures a and b of the relay LR, are connected through the channel bus bar CB, to the line amplifier LA,, the radio transmitter ST, and the transmitting antenna TA,. Therefore, when the line relay LR, and the relay R, become energized the main transmission circuit between the studio A and the transmitting station associated with the bus bar CB, becomes closed. Furthermore the lamp L at the studio indicates to the announcer that the. relay R, has operated. Similarly the lamp L,,, at the control room indicates to the operator thereat that the line relay LR, has also operated. The circuit of lamp L,,, includes the battery B lamp L,,, the armature c of the relay LR, and ground, The relay R, at studio A may be deenergized by operating key K key K,, or key K17, these keys all being included in a series path which includes the winding of the relay R,. Keys K,, and K, are also in series with the windings of relays R R and 1%,, and hence are the studio and control room master release keys, respectively.

In order that the announcer at studio A may know that one or more of the transmitting stations are ready to receive a pro ram, lamps L, to L,, inclusive, are provided. hese are located in the studio, each lam being associated with one of the transmitting stations, each lamp being also associated with one of the relays R, to R inclusive. Lamps L, to L, at studio A, lamps L, to L, at studio B and lamps L, to L, at studio C are controlled by signal keys SK, to SK,, respectively, which are located in the control room, and which are under the su ervision and con trol of the operator at t e control room. Furthermore, means are provided so that by the operation of one of the relays, such as relay R, in studio A, the lamps L, and L, in studios B and C, corresponding to the relays R, and R,",respectively,in these studios,will become extinguished. Thus the light L, advises the announcer in studio A that the carrier wave of the transmitting station assoiated with the channel bus bar GB, is on the air and that the transmission system to that transmittin station is ready for service from studio A. By operating one of the signal keys such as key SK,, the lamp L associated with this key becomes illuminated by the flow of current from battery 13 through the lamp L,,, the key SK, and ground. The. lamp L, also becomes illuminated regardless of the state of energization of the relay R,, aswill be shown more clearly hereinafter. When the winding of the rela R, is deenergized current flows from the attery B, through the armature of the relay 1B,, conductor 21, contact f and armature B of the relay R,, the lamp L,, key SK, and round. When the winding of the relay R, ecomes energized, current then flows from the battery B through the key K conductor 23, the key K,,, contact 6 and armature B of the relay R,, lamp L,, key SK, and ground. Similarly the lamps L, and L," are operated by the key SK, with current from battery B,, when the corresponding relays R, and R," in studios A and B, are deenergized. Yetwhenthe winding of the relay R, in studio A becomes energized the corresponding lam s L, and L, in studios B and C, respective y, become extinguished, while lamp L, in studio A remains illuminated. This therefore indicates to the announcers in studios B and C that the transmitting station corresponding to the channel bus bar GB, is not available for transmission from studios B and C. Obviously when relay R, again becomes deenergized,al ofthelamps L,, L, and L," in the various studios again become illuminated, therefore indicating that the transmitting station correspondin to the channel bus bar GB, is again availa le for transmission from any one of these studios. p

Keys K, and K K,, and K,,, K,," and K,, are the master release keys, keys K,,,

K,,' and K,," being under the supervision.

and control of the announcers in studios A, B and C, respectively, and keys K K,, and K,," being under the supervision and control of the operator at the control room. The keys at the various studios permit the announcers at these studios to release any one or more of the transmitting stations from the studio under the control of a particular announcer. The keys K K and K,," at the control room break the circuits of the batteries B B and B thereby releasing the relays R, to R,, R, to R, and R, to R, in the studios A, B and C, respectively. The keys K,,, K,, and K,," at the various studios operate in a similar manner. This enables either the announcer in the studio or the operator in the control room to simultaneously release all of the transmitting stations connected to his (the announcers) studio.

The apparatus at the studios A, B and C accomplish primarily the following: First, a suitable arrangement is provided whereby the amplifiers CA, to CA inclusive, at the control room may be connected to the corresponding announcers microphones MA, to

MA the program microphones MP, to MP or to the microphones at distant points to which the nemo circuits NC, to N0 respectively, are connected; second, the announcers at the various studios are equipped to pick up or release any one or more of the transmitting stations which are connected to the channel bus bars CB, to CB,, inclusive; third, lamps are provided in the various studios so that the announcers in these studios may know what transmitting stations are available to transmit the program matter; and fourth, lamps are provided throughout the studios and the control room to indicate to the studio announcers and the control room operator whether or not the relays have properly operated.

In studio A the output of the announcers microphone MA, passes through the microphone control equipment CP, to the lower contacts j and k of the switch K whereas the output of the program microphone MP, similarly passes through the microphone control equipment CF, to the lower contacts j and k of the switch K,,. The nemo circuit NC, is connected to the upper contacts a and b of the switch K The upper contacts a and b of the switch K, are connected to the blades 6 and f of the switch K The blades 6 and f of the switch K, are connected to the input of the amplifier CA, at the control room. \Vhen the switch K, is thrown downwardly to engage contacts j and k, the announcers microphone MA, is then connected to the input of the amplifier CA,. By throwing the switch K, upwardly to engage contacts a and b, and switch K downwardly to engage contacts j and k, the program microphone MP, is then connected to the input of the amplifier CA,. By throwing both switches K and K to the upward positions, the nemo circuit NC, is then connected to the input of the amplifier CA,. By leaving switch K in its upward position, by operating switch K the announcer at studio A may connect the announcers microphone MA,, or the nemo circuit NC,, to the input of the amplifier CA,.

A lamp L, is located in studio A and provides an indication to the announcer at studio A that the equipment of the control room corresponding to studio A is in readiness for operation. It will be understood that this lamp L, may, if desired, be a colored lamp to distinguish this lamp from all the other lamps. By closing key K,,, the control room operator sends current from battery 13., through the lamp L,,, the circuit including battery B key K,,,. conductor 27, lamp L, and ground. Another lamp, L which is located at the control room, is also operated by key K The lamp L, similarly indicates to the operator at the control room that the apparatus at the control room corresponding to the studio A is in readiness for operation. The circuit of the lamp L,,- includes the battery 13,, key K lamp L, and ground. It is to be noted that the winding of the main relay R can not become energized unless the key K in the control room has first operated. This therefore prevents the announcer at studio A from transmitting his program to one or more of the transmitting stations before the proper connections have been made in the control room.

A lamp L is located at studio A and provides a visible means of indication to the announcer at that studio that he is wanted on a telephone intercommunicating system (not shown). This lamp L, is operated by key K1,, at the control room. By operating key K current flows from the battery B through key K,,,, the conductor 28, lamp L and ground.

Relays SR, to SR,, inclusive, are provided at the control room so that when the corresponding line amplifiers LA, to LA, are ready for use but are not connected to a studio bus bar the inputs of these line amplifiers will be short-circuited. In other words,

when the relays LR, to LR,, inclusive, are not energized, relays SR, to SR-.,, inclusive, will be operated. More specifically the relays SR, to SR, will be operated when the line relays corresponding to the various 1" the sake of simplicity the operation of only one of the relays, SR will be considered. One terminal of the winding of the relay SR 1 is connected to ground through conductor 29 through the middle contact of the key SK The other terminal of the winding of the relay SR is connected to the battery B through conductor 30, conductor 21 and the armature of the relay 1R Therefore upon the operation of the key SK current flows from battery 13 through the winding of the relay SR thereby operating said relay. The armature of the relay SR is then attracted providing a short-circuit for the input of the amplifier LA,. The relay SR is always operated to put a short circuit on the input of the amplifier LA when the key SK, is operated, and when, also, the winding of the relay IR is not energized. WVhen the winding of the relay 1R becomes energized, as, for example, when relay R in studio A becomes energized, the circuit connecting battery B and the winding of the relay SR is opened, deenergizing the winding of relay SR removing the short-circuit from the input of the amplifier LA and placing this channel in an operative condition. Similarly relays SR SR and SR are energized by current from battery B. through the armatures of relays IR IE and IR the conductors 31, 32 and 33, the conductors 34, 35 and 36, the windings of the relays SR SR and SR the conductors 37, 38 and 39, the middle contacts of keys SK SK and SK, respectively. and ground.

The main relays R R and R open the main transmission paths between studios A A, B and C, and the studio bus bars SE SE and S13 respectively, when it is considered undesirable to transmit that which is taking place in these studios. Confining the description of the apparatus at the control room corresponding to the studio A and to that in studio A it is apparent that one terminal of the winding of the relay R is grounded and that the other terminal of the winding of the relay R is connected through conductor 40 to the contacts 0 and e, of the switch K The blade 9 of the switch K is connected to the battery B through conductor 27 and key K when key K is closed. Furthermore, when key K is closed, the operation of switch K to close either of contacts 0 or 6 permits current to flow from battery B through conductors 27 and 40 and through the winding of the relay R When the winding of the relay R becomes energized, one of its armatures a closes a contact which permits current to flow from battery B through lamp L the armature a of the relay R and ground. This lamp indicates to the operator at the control room whether or not the relay R has operated. Moreover the contacts b and 0 of the relay R control the main ransmission path between the amplifier CA,

and the studio bus bar SB When the winding of the relay R is not energized the armature d of said relay short-circuits the studio bus bar 5B thereby short-circuiting the line amplifiers connected thereto.

When key K is operated, causing lamp L to be illuminated as an indication to the announcer in studio A that everything in the control room is in readiness for transmission from studio A, and when switches K and K are operated to connect the program microphone MP the announcers microphone MA or the nemo circuit N0 to the input of the amplifier CA either lamp L L L is illuminated to indicate to the announcer whether the program microphone MP the announcers microphone MA or the nemo circuit N0 respectively, is connected to the input of the amplifier CA The circuit for lamp L is as follows: battery B key K conductor 27, blade h and blade 61 of switch K blade and blade 6 of switch K lamp L and ground. The circuit for lamp L is as follows: battery B key K conductor 27, blade 71. and blade m of switch K lamp L and ground. Similarly the circuit for lamp L is as follows: battery B key K conductor 27 blade 72.

and blade at of switch K blade g and blade 0 of switch K lamp L and ground.

A relay R controls a signal lamp L which is a visible indication to the operator at the control room that the anouncer at studio A has set up his equipment so as to transmit the program coming over the nemo circuit NC The winding of the relay R is connected to a battery B through a conductor 41 and the blades d and h of the switch K Inasmuch as the switch K must be thrown to its upward position to connect the nemo circuit NC to studio A, the relay R, will thereupon become energized, illuminating the lamp L, by the flow of current therethrough from the batery B Similar arrangements are provided in the control room in connection with studios B and C.

The line relays LR to LR inclusive, are so arranged that the input of the amplifiers LA to LA inclusive, may be switched from one studio bus bar, such as SE to any one or the other of the studio bus bars, such as SE and 8B,. This has been explained hereinabove. Yet in each of these line relays, such ing of the relay R in studio A. These wind.- ings are in parallel relationship with each other and consequently are simultaneously energized or deenergized.

The phrase transmitting station as employed herein designates a radio transmitter, public address equipment, an individually located loud speaker or any other suitable signaling circuit. The word studio as employed herein designates a. place where a program of news, music or any other sound originates, whether it be in a room adjacent to the control room or at some point distant from the control room requiring a connection thereto by local or long distant telephone lines or any other suitable signaling medium.

While only three studios and four transmitting stations have been shown and described in Figs. 4 and 5, it will be understood that the system is adaptable to connect any number of studios and any number of transmitting stations within the scope of the invention.

While no auxiliary equipment, such as equalizers, repeating coils, jacks, artificial lines, etc., not absolutely essential to the opoperation of the system, are shown herein, it is to be understood that they may be added, as they are found desirable, in any manner well known to the art without departing from the spirit of the invention or the scope of the appended claimsx lVhile the invention has been disclosed in certain particular embodiments herein merely for the purpose of illustration, it is to he understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

lVhat is claimed is:

1. In a multiplex broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations, :1 control room interconnecting said studios and said transmitting stations wherein may be controlled the transmission of the programs of said studios through said transmitting stations, and a plurality of indicating devices to indicate in said control room and in each studio which transmitting stations are available for program transmission.

2. In a multiplex broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations, a control room for controlling the transmission of the programs of said studios through said transmitting stations, a plurality of indicating devices in said control room and in each studio to indicate which transmitting stations are available for program transmission, and means for preventing the simultaneous transmission of the programs of more than one studio through any one transmitting station.

3. In a radio broadcasting system, a plurality of studios wherein broadcasting programs originate, a plurality of transmitting stations, a plurality of groups of relays one group corresponding to each studio, one relay in each group corresponding to each transmitting station, means for energizing said relays so as to transmit the programs of said studios simultaneously through said transmitting stations, and means whereby not more than one of said relays corresponding to one of the transmitting stations may be energized at the same time.

4. In a multiplex broadcasting system, a plurality of program sources, a plurality of transmitting stations, means for interconnecting said program sources and said transmitting stations so as to control the trans mission of the programs of said program sources through said transmitting stations, and a plurality of groups of indicating devices, one group corresponding to each transmitting station, one indicating device in each group appearing at each program source, said indicating devices indicating which transmitting stations are available for program transmission, said indicating devices also indicating which program sources are available to said program transmitting stations for transmission of the programs thereof.

5. In a multiplex broadcasting system, a plurality of program sources, a plurality of transmitting stations, means for interconnecting said program sources and said transmitting stations so as to control the transmission of said programs through said transmitting stations, and a plurality of indicating devices located at the Various program sources so that those people working with any particular program source may know at any time what transmitting stations are associated with that program source.

6. In a multiplex broadcasting system, a plurality of program sources, a plurality of transmitting stations, and means interconnecting said program sources and said transmitting stations so as to control the transmission of the programs of said program sources through said transmitting stations, and a plurality. of indicating devices one located at each program source and one located at the control room so that the people working at said program sources and at said control station may know which program sources are transmitting programs and which transmitting stations are transmitting the programs of said program sources.

7. In a multiplex broadcasting-system, a plurality of program sources, a plurality of transmitting stations, a control room including means for interconnecting said program sources and said transmitting stations so as to control the transmission of said programs through said transmitti g stations, and a signaling system interconnecting said program sources and said control room so that the operator at any program source may signal the operator at the control room Without disturbing the transmission between said program sources and said transmitting stations, and vice versa.

In testimony whereof, We have signed our names to this specification this 16th day of August 1926.

EDMUND R. TAYLOR. OSCAR B. HANSON.

References Cited Ryan Smythe at a11,499,081 Clark et a1 1,594,454 

